When you work on "antique" radios, you can't exactly ring-up the manufacturer and order replacement parts, so you tend to hoard things that most people would consider rubbish. It may seem like odd behavior for otherwise reasonable people, but it is completely rational; you never know when you or a friend might need the epicyclic reduction drive off of the tuning condenser for a 1938 Philco. It's always nice to have a few on-hand.
But, left unchecked, the hoard will eventually grow to an unmanageable size. If you forget that you've got that 1938 Philco carcass in the junk pile, what good is having it at all? None. Like it or not, you have to occasionally thin the herd. Unfortunately, that requires making some hard, cold-blooded choices.
Such was the case with this Zenith Y-723 with the cracked case and partially disassembled chassis. It had already given up a number of parts so that other sets could live on, but I was still having a hard time with the idea of pitching it.
Then the thought occurred to me: The tuning mechanism and it's associated LC components are still there, Why not build a "modern" radio around them?
Normal people don't think of things like that, and only a real whack job would actually do it.
And with that thought, I present to you: The Zenith Y723-2017!
The salvaged tuning section from the defunct Y723 found itself sharing a chassis (fabricated from scrap ductwork) with a power supply built around the transformer from an old Motorola desk charger. Below the chassis is the RF/AF circuitry; the radio is based on the TA2003 IC, and the audio amplifier uses a Sanyo LA4425A.
The speaker is a 3 1/2" model of unknown origin, another junkbox treasure. I'm a big fan of these mid-50's Zeniths, but have to admit that their tone sounds a lot like the plastic case. So, to get away from that, I built an MDF enclosure for the speaker, hoping that it absorbs some of that cabinet resonance. The new chassis and speaker box fit snuggly into the original cabinet, which remains cracked, albeit reinforced internally with lots of hot-glue.
How's it work? Great! AM reception is on par with the original set, but FM is significantly better: It's far more sensitive and just plain sounds better. The LA4425A delivers enough audio to drive the orphan speaker loud enough to fill a room, and the audio doesn't sound like it's originating from a plastic cave.
That said, the low-frequency response of the orphan speaker was a bit limited, so I retroactively cobbled-in a Baxandall tone circuit built around one section of a LM324 quad op-amp. This is adjusted internally; I didn't bring the controls out because I envision it as serving only to equalize the audio response, not as something I'd be playing with.
I'm still not sure what I'll do with this, but I won't be throwing it out anytime soon.
But, left unchecked, the hoard will eventually grow to an unmanageable size. If you forget that you've got that 1938 Philco carcass in the junk pile, what good is having it at all? None. Like it or not, you have to occasionally thin the herd. Unfortunately, that requires making some hard, cold-blooded choices.
Such was the case with this Zenith Y-723 with the cracked case and partially disassembled chassis. It had already given up a number of parts so that other sets could live on, but I was still having a hard time with the idea of pitching it.
Then the thought occurred to me: The tuning mechanism and it's associated LC components are still there, Why not build a "modern" radio around them?
Normal people don't think of things like that, and only a real whack job would actually do it.
And with that thought, I present to you: The Zenith Y723-2017!
How's it work? Great! AM reception is on par with the original set, but FM is significantly better: It's far more sensitive and just plain sounds better. The LA4425A delivers enough audio to drive the orphan speaker loud enough to fill a room, and the audio doesn't sound like it's originating from a plastic cave.
That said, the low-frequency response of the orphan speaker was a bit limited, so I retroactively cobbled-in a Baxandall tone circuit built around one section of a LM324 quad op-amp. This is adjusted internally; I didn't bring the controls out because I envision it as serving only to equalize the audio response, not as something I'd be playing with.
I'm still not sure what I'll do with this, but I won't be throwing it out anytime soon.
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